Anisotropically flexible vibration isolating coupling mechanism

ABSTRACT

A flexible coupling mechanism may be used to suspend a structural component, such as a propulsion pod, from a support member, such as a strut of a hydrofoil watercraft. The flexible coupling mechanism may include multiple vibration isolating mounts configured to extend through the support member to suspend the structural component. The vibration isolating mounts may include a plurality of elastomeric bushings configured to prevent direct contact between a component rigidly coupled to the support member and a component rigidly coupled to the structural component. The elastomeric bushings may include a tapered outer profile configured to provide a nonlinear force feedback profile in response to rotation of the support member relative to the structural component.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference under 37 CFR 1.57.

This application claims the benefit of U.S. Provisional Application No.63/079,909, filed Sep. 17, 2020, the disclosure of which is herebyincorporated by reference in its entirety.

BACKGROUND Technical Field

The disclosed technology relates generally to vibration isolatingmounts, and in particular to vibration isolating mounts which may beused to provide a coupling mechanism which can be anisotropicallyflexible in various directions.

Description of Related Technology

Weight-shift controlled watercraft can include a hydrofoil coupled to asupporting platform or board. A user positioned on the supportingplatform can control the operation of the weight-shift controlledwatercraft by shifting their weight on the board. To provide aweight-shift controlled watercraft which is responsive to thecontrolling motions of a user, many weight-shift controlled watercraftemploy rigid couplings between various structural component, as acompletely rigid coupling is viewed as providing a superior ridingexperience.

Because the hydrofoil and other components of the watercraft may besubstantially heavier and denser than a board comprising a buoyantinternal material, noises and vibrations generated by operation of thewatercraft may be amplified by the board. In addition, the use of rigidcoupling between the various components of the watercraft may facilitatethe transmission of noise and vibrations from the driving motor to theboard and may amplify the noise and vibration.

SUMMARY

In one broad aspect, a watercraft device is provided including a supportplatform; a strut extending from the underside of the support platform;a hydrofoil connected to the strut; and a propulsion pod supported bythe strut at a location in-line with or above the hydrofoil, thepropulsion pod secured to the strut by an anisotropically flexiblecoupling mechanism including a plurality of vibrationally isolatedmounts extending through the strut, each of the plurality ofvibrationally isolated mounts rigidly coupled to the propulsion pod attwo locations on opposite sides of the strut.

Each of the plurality of vibrationally isolated mounts may include arigid internal axially extending member configured to be rigidly coupledto the propulsion pod; and an elastomeric bushing radially outward ofthe axially extending member, the elastomeric bushing configured toretain the axially extending member, the elastomeric bushing includingan inner abutment surface dimensioned to contact at least one of thestrut or a retaining component rigidly coupled to the strut. Each of theplurality of vibration isolating mounts may include a first elastomericbushing disposed at least partially on a first side of the strut; and asecond elastomeric bushing disposed at least partially on a second sideof the strut opposite the first side of the strut. The first and secondelastomeric bushings may be axially aligned with one another, and theaxially extending member may extend through both the first and secondelastomeric bushings.

Each of the elastomeric bushings may include a radially inward portionhaving a first cross-sectional diameter, the radially inward portiondimensioned to extend at least partially into a mounting aperture in thestrut; and a radially outward portion including the inner abutmentsurface and having a second cross-sectional diameter greater than thefirst cross-sectional diameter. A radially outward portion of an outerend of each of the plurality of elastomeric bushings may include abeveled shoulder section.

The outer portion of each of the plurality of elastomeric bushings maybe shaped shaped to provide a non-linear restoring force response as thestrut is rotated relative to the propulsion assembly about a roll axisof the propulsion hub. Each of the elastomeric bushings may include aninternal rigid sleeve surrounded by an elastomeric sleeve locatedradially outward of the internal rigid sleeve.

The anisotropically flexible coupling mechanism may be configured toprovide less resistance to rotation of the strut relative to thepropulsion assembly about a roll axis of the propulsion assembly than torotation of the strut relative to the propulsion assembly about a pitchaxis of the propulsion hub.

The watercraft device may additionally include a battery pack disposedat least partially within the support platform. An elastomeric materialmay be disposed between the battery pack and the support platform. Thestrut may include a first plug component and the battery pack mayinclude a second plug component, the first and second plug componentsconfigured to engage with one another to form an electrical connectionbetween the battery pack and the strut, and at least one of the firstplug component or the second plug component may include an elastomericmaterial. An upper surface of the battery assembly may be flush with asurrounding upper surface of the support platform. The coupling betweenthe battery assembly and the strut may reduce an intensity of vibrationstransmitted to and attenuated by the support platform.

The watercraft device may additionally include an elastomeric materialdisposed between a mounting plate of the strut and a mounting surface onthe underside of the support platform, the mounting plate of the strutcoupled to the support platform by a plurality of rigid fasteners. Thewatercraft device may be configured to reduce generation of noise havingfrequencies in the range of 300 Hz to 3 kHz.

The watercraft device may include a motor controller operably connectedto the motor, the motor controller configured to provide a nonlineartransition rate between motor speeds, the nonlinear transition rateconfigured to minimize vibration generation. The nonlinear transitionrate may be a predetermined nonlinear transition profile which minimizesmotor operation at speeds which generate forcing frequenciescorresponding to resonant frequencies of components of the watercraftdevice. The nonlinear transition rate may be dynamically adjusted inresponse to generated vibration.

In another broad aspect, a weight-shift controlled watercraft device isprovided, including a board configured to support a rider thereon; astrut extending from the underside of the board, the strut having ahydrofoil supported at a lower end of the strut; a propulsion podincluding a propeller operably coupled to a driving motor; a housing,the strut extending through a portion of the housing, and a plurality ofvibration isolating mounts flexibly coupling the propulsion assembly tothe strut, each of the plurality of vibration isolating mounts includinga fastener extending from a first side of the strut to a second side ofthe strut through an aperture in the strut; and an elastomeric bushingsurrounding at least a portion of the fastener, the elastomeric bushingin contact with at least one of the strut or a retaining componentrigidly coupled to the strut to provide vibration isolation between thepropulsion pod and the strut.

The plurality of vibration isolating mounts may be configured to suspendthe propulsion pod from the strut. The plurality of vibration isolatingmounts may be configured to prevent direct contact between a mountingcomponent rigidly coupled to the strut and a mounting component rigidlycoupled to the propulsion pod. The elastomeric bushing may include aninner abutment surface configured to contact at least one of the strutor a retaining component rigidly coupled to the strut to provide arestoring force in response to roll of the strut relative to thepropulsion pod about a rotational axis of a propeller of the propulsionpod. The inner abutment surface may be radially spaced apart from aradially inward portion of the elastomeric bushing.

In another broad aspect, a weight-shift controlled watercraft device isprovided, including a board; a propulsion assembly coupled to the board,the propulsion assembly including a strut extending from the undersideof the board; a hydrofoil supported at a lower end of the strut; apropulsion pod supported by the strut, the propulsion pod including apropeller operably coupled to a driving motor, and a housing dimensionedto allow the strut to extend therethrough; and a flexible couplingmechanism coupling the propulsion pod to the strut, the couplingmechanism configured to reduce vibration transfer between the propulsionpod and the board.

The coupling mechanism may include a plurality of vibration isolatingmounts securing the propulsion pod to the strut, and each of theplurality of vibration isolating mounts may include a fastener extendingfrom a first side of the propulsion pod housing to a second side of thepropulsion pod housing through an aperture in the strut; and anelastomeric bushing surrounding at least a portion of the fastener, theelastomeric bushing in contact with at least one of the strut or aretaining component rigidly coupled to the strut to provide vibrationisolation between the propulsion pod and the strut.

The propulsion pod housing may include a first strut aperture and asecond strut aperture extending therethrough, the first and second strutapertures dimensioned to allow sections of the strut to extendtherethrough and prevent direct contact between a rigid portion of thestrut and a rigid portion of the propulsion pod housing. The propulsionpod housing may include a gasket disposed within one of the first orsecond strut apertures in the propulsion pod housing to reducehydrodynamic drag on the propulsion pod housing, the gasket including anelastomeric material. The propulsion pod housing may include ahydrodynamic deflector located fore of at least one of the first orsecond strut apertures in the propulsion pod housing to reducehydrodynamic drag on the propulsion pod housing.

The vibration reduction mechanism may include a motor controlleroperably connected to the motor and configured to provide a nonlineartransition profile during changes in motor speeds, the nonlineartransition profile minimizing motor operation at speeds which generateforcing frequencies corresponding to resonant frequencies of componentsof the watercraft device.

In another broad aspect, an anisotropically flexible coupling mechanismis provided, the anisotropically flexible coupling mechanism configuredto flexibly couple a suspended component to a support member extendingtherethrough, the coupling mechanism including a plurality of vibrationisolating suspension mounts configured to extend through apertures inthe support member, each of the vibration isolating suspension mountsincluding a rigid internal member extending along a longitudinal axis;and an elastomeric sheath surrounding the axially extending member, theelastomeric sheath including a radially inward portion surrounding therigid internal member; and a radially outward portion spaced at leastpartially apart from the radially inward portion, the radially outwardportion including an abutment surface configured to contact at least oneof the support member or a component rigidly coupled to the supportmember.

The abutment surface of the elastomeric sheath may be generallyorthogonal to the longitudinal axis of the rigid internal member. Theapertures in the support member may be generally parallel to one anotherand axially offset from one another. The rigid internal member may beconfigured to be rigidly coupled to the suspended component at twolocations on opposite sides of the support member.

In another broad aspect, a watercraft is provided, including a supportplatform configured to support at least one passenger; a propulsionmechanism; and a vibration isolating mount flexibly coupling thepropulsion mechanism to the support platform, the vibration isolatingmount configured to prevent direct contact between a component rigidlycoupled to the support platform and a component rigidly coupled to thepropulsion mechanism to inhibit direct translation of vibration from thepropulsion mechanism to the support platform.

The vibration isolating mount includes an elastomeric structureconfigured to prevent direct contact between a component rigidly coupledto the support platform and a component rigidly coupled to thepropulsion mechanism. The elastomeric structure may include anelastomeric sheath.

An inner surface of the elastomeric sheath may be in contact with aportion of the propulsion mechanism or a component rigidly coupled,either directly or indirectly, to the propulsion mechanism, and where anouter surface of the elastomeric sheath may be in contact with a portionof the support platform or a component rigidly coupled, either directlyor indirectly, to the support platform. The portion of the propulsionmechanism or the component rigidly coupled to the propulsion mechanismmay extend through an aperture in a portion of the support platform orthe component rigidly coupled to the support platform.

An inner surface of the elastomeric sheath may be in contact with aportion of the support platform or a component rigidly coupled, eitherdirectly or indirectly, to the support platform, and where an outersurface of the elastomeric sheath may be in contact with a portion ofthe propulsion mechanism or a component rigidly coupled, either directlyor indirectly, to the propulsion mechanism. The portion of the supportplatform or the component rigidly coupled to the support platform mayextend through an aperture in a portion of the propulsion mechanism orthe component rigidly coupled to the propulsion mechanism.

The watercraft may include a personal watercraft configured to support asingle operator. The watercraft may include a jetski. The watercraft mayinclude a watercraft configured to carry a plurality of passengers. Thewatercraft may include a boat. The component rigidly coupled to thesupport platform may include a transom of the boat.

The support platform may include a closed hull of the watercraft. Thesupport platform may include an open hull of the watercraft.

The propulsion mechanism may include an outboard motor. The propulsionmechanism may include a propeller. The propulsion mechanism may includean electric motor. The propulsion mechanism may include an internalcombustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several embodiments in accordance with thedisclosure and are not to be considered limiting of its scope, thedisclosure will be described with additional specificity and detailthrough use of the accompanying drawings. In the following detaileddescription, reference is made to the accompanying drawings, which forma part hereof. In the drawings, similar symbols typically identifysimilar components, unless context dictates otherwise.

FIG. 1A is a perspective view of an assembled weight-shift controlledhydrofoil watercraft. FIG. 1B is a side view of the hydrofoil watercraftof FIG. 1A. FIG. 1C is a front view of the hydrofoil watercraft of FIG.1A. FIG. 1D is a top plan view of the hydrofoil watercraft of FIG. 1A.FIG. 1E is a bottom plan view of the hydrofoil watercraft of FIG. 1A.

FIG. 2A is a partially exploded perspective view of a hydrofoilwatercraft such as the hydrofoil watercraft of FIG. 1A, illustrating amodular design of certain components of the hydrofoil watercraft. FIG.2B is a perspective view of the propulsion assembly and battery pack ofthe hydrofoil watercraft of FIG. 2A, shown in a detached state. FIG. 2Cis a perspective view of the propulsion assembly and battery pack of thehydrofoil watercraft of FIG. 2A, shown in an assembled state. FIG. 2D isa perspective of the hydrofoil watercraft of FIG. 2A, shown in apartially assembled state in which the propulsion assembly is attachedto the board.

FIG. 3A is a perspective view of another embodiment of a propulsionassembly which includes an elastomeric vibration isolating component.FIG. 3B is a perspective view of another embodiment of a battery packwhich includes an elastomeric vibration isolating component.

FIG. 4A is an exploded isometric view of a strut with an adaptive clampshown. FIG. 4B is another exploded view of the strut and adaptive clampof FIG. 4A. FIG. 4C is an assembled view of the strut and adaptive clampof FIG. 4A. FIG. 4D is a cross-sectional view of the assembled strut andadaptive clamp of FIG. 4C.

FIG. 5A is a perspective view of an embodiment of an elastomeric bushingwhich can be used as part of a flexible coupling between a propulsionpod and a strut. FIG. 5B is an isometric exploded assembly view of theelastomeric bushing of FIG. 5A. FIG. 5C is a front view of theelastomeric bushing of FIG. 5A. FIG. 5D is a cross-sectional view of theelastomeric bushing of FIG. 5A, taken along the line D-D of FIG. 5C.

FIG. 6A is an exploded isometric view of an embodiment of a propulsionassembly in which a propulsion pod is secured to a housing via aplurality of vibrationally-isolated through-pins. FIG. 6B is an explodedview from in front and above the embodiment of FIG. 6A. FIG. 6C is anisometric view of the assembled propulsion assembly of FIG. 6A. FIG. 6Dis a cross-sectional view of the assembled propulsion assembly of FIG.6C, taken along a plane extending through the longitudinal axes of twovertically aligned through-pins. FIG. 6E is a detail cross-sectionalview of section B of FIG. 6D.

FIG. 7 is a front view of a hydrofoil watercraft undergoing strut rollrelative to the propulsion housing.

FIG. 8A is an exploded isometric view of another embodiment of apropulsion assembly in which a propulsion pod is secured to a housingvia a plurality of vibrationally-isolated through pins. FIG. 8B is anexploded front view of the embodiment of FIG. 8A. FIG. 8C is anisometric view of the assembled embodiment of FIG. 8A.

FIG. 9A is an exploded isometric view of another embodiment of apropulsion assembly in which a propulsion pod is secured to a housingvia a plurality of vibrationally-isolated through-pins. FIG. 9B is anexploded view from in front and above the embodiment of FIG. 9A. FIG. 9Cis a cross-sectional view of the assembled propulsion assembly takenalong a plane extending through the longitudinal axes of two verticallyaligned through-pins. FIG. 9D is a detail cross-sectional view ofsection D of FIG. 9C. FIG. 9E is an isometric view of the assembledpropulsion assembly of FIG. 9A. FIG. 9E is an isometric view of theassembled propulsion assembly of FIG. 9A.

FIG. 10A is an exploded isometric view of another embodiment of apropulsion assembly in which a propulsion pod is secured to a housingvia a plurality of vibrationally-isolated through pins. FIG. 10B is anexploded view from above and in front of embodiment of FIG. 10A. FIG.10C is an isometric view of the assembled embodiment of FIG. 10A.

FIG. 11A is a plot of measured noise as a function of frequency,illustrating a reduction in noise achieved by the use of a vibrationisolating mounting structure in comparison to a non-isolating mountingstructure. FIG. 11B is another plot of measured noise as a function offrequency, illustrating reductions in noise achieved by the use ofvibration isolating mounting structures in comparison to a non-isolatingmounting structure.

FIG. 12A is a perspective view of a combination propulsion pod andhydrofoil structure, coupled to a strut at the base of the strut. FIG.12B is an exploded assembly view of the combination propulsion pod andhydrofoil structure of FIG. 12A shown detached from the strut.

FIG. 13 is a cross-sectional view schematically illustrating anotherembodiment of a combination propulsion pod and hydrofoil structure,coupled to a strut at the base of the strut. is a cross-sectional viewschematically illustrating another embodiment of a combinationpropulsion pod and hydrofoil structure, coupled to a strut at the baseof the strut.

DETAILED DESCRIPTION

Examples of weight-shift controlled watercraft are described in, forexample, U.S. Pat. No. 10,797,118, which hereby incorporated byreference in its entirety.

FIG. 1A is a perspective view of an assembled weight-shift controlledhydrofoil watercraft. FIG. 1B is a side view of the hydrofoil watercraftof FIG. 1A. FIG. 1C is a front view of the hydrofoil watercraft of FIG.1A. The hydrofoil watercraft 100 includes a board 110 for supporting arider. The hydrofoil watercraft 100 also includes a strut 130 extendingaway from a lower surface 112 of the board 110. In the illustratedembodiment, the strut 130 supports a hydrofoil 140 coupled to the strut130 at a hydrofoil coupling point 136, and a propulsion pod 150 coupledto the strut 130 at a propulsion pod coupling point 134. The strut 130,along with the hydrofoil 140 and propulsion pod 150 supported by thestrut 130, form a propulsion assembly 160. In the illustratedembodiment, the hydrofoil coupling point 136 is located at or near thebase of the strut 130 and the propulsion pod coupling point 134 islocated between the board and the hydrofoil coupling point 136.

As discussed in greater detail elsewhere herein, the couplings betweenthe strut 130 and the hydrofoil 140 and the propulsion pod 150 may bemade in any suitable manner. In some embodiments, the hydrofoil 140and/or the propulsion pod 150 may be partially or wholly integral withthe strut. In some embodiments, intermediate coupling structures may beused to facilitate a desired coupling arrangement between the hydrofoil140 and/or the propulsion pod 150 and the strut 130. In someembodiments, the hydrofoil 140 may be integral with the propulsion pod150, such that the wings of the hydrofoil extend from the propulsion pod150 itself, rather than being part of a discrete structure.

Many embodiments of hydrofoil watercrafts include a rigid couplingbetween the propulsion system and the strut, and similarly rigidcouplings between strut and board. In a weight-shift controlled system,such a rigid coupling may be intended to provide stability and tightercontrol over the operation of the hydrofoil watercraft and improve theperformance of the watercraft. A rigid coupling may be expected toprovide more responsiveness to a rider during operation.

FIG. 1A also illustrates principal axes of the hydrofoil watercraft 100,shown relative to the propulsion pod 150. The roll axis of the hydrofoilwatercraft 100 is illustrated as aligned with the longitudinal axis ofthe propulsion pod 150 and in particular with the axis of rotation ofthe propeller 102. The pitch axis of the hydrofoil watercraft 100 isperpendicular to the roll axis. The yaw axis of the hydrofoil watercraft100 is coplanar with the roll axis of the hydrofoil watercraft 100 andwith the longitudinal axis of the strut 130. However, the yaw axis ofthe hydrofoil watercraft 100 may in some embodiments be oriented at anangle to the longitudinal axis of the strut, depending on the design ofthe strut 130 and the hydrofoil 140. For example, in other embodiments,a longitudinal axis of the strut 130 is oriented at an oblique angle tothe longitudinal axis of the propulsion pod 150, rather than a rightangle. In such an arrangement, there may be a non-zero angle between thelongitudinal axis of the strut 130 and the yaw axis of the hydrofoilwatercraft 100.

The hydrofoil 140 will generate lift as the hydrofoil watercraft 100moves through the water. Depending on the amount of lift generated bythe hydrofoil 140, the hydrofoil watercraft 100 can operate in anon-foiling mode, a planing mode, or a foiling mode. In the non-foilingmode, the board 110 is in contact with the surface of the water, and thebuoyancy of the board 110 supports the hydrofoil watercraft 100 and therider. In the planning mode, any lift generated by the hydrofoil 140 isinsufficient to overcome the weight of the hydrofoil watercraft 100, andthe board 110 may remain generally in contact with the water as thehydrofoil watercraft 100 moves through the water. When operating infoiling mode, the lift generated by the hydrofoil 140 is sufficient tolift the board 110 away from the surface of the water and support theweight of the hydrofoil watercraft 100 and rider. As described in U.S.Pat. No. 10,797,118, the hydrofoil watercraft 100 may be designed toprovide a smooth transition between these different modes of operation.

In contrast to watercraft driven by internal combustion engines such asoutboard motors, which may generate a substantial amount of noise, ahydrofoil watercraft may be driven by a comparatively quieter electricmotor. However, the various components of a hydrofoil watercraft drivenby an electric motor, such as the motor itself, the driven propeller,the gearbox, and other components of the hydrofoil watercraft, willstill generate noise. Certain frequencies of noise and vibrationgenerated by the components of the hydrofoil watercraft may bepropagated via the strut 130 to which the propulsion pod 150 is rigidlycoupled, and may subsequently be amplified by the surrounding board 110.

The operation of the hydrofoil watercraft may result in the generationof noise within the range of human hearing, and the transmittedvibrations may also be felt by the rider. As human hearing isparticularly sensitive to sounds with frequencies between 300 Hz and 3kHz, a hydrofoil watercraft which reduces the volume of generated noisein the range of 300 Hz and 3 kHz, and which minimizes vibrations, mayprovide a more pleasant operating experience. This reduction in audiblenoise and vibration could allow, for example, conversations between twohydrofoil watercraft riders riding near each other, even when operatingin foiling mode.

In some embodiments of hydrofoil watercrafts, one or more vibrationisolating components may be provided between the propulsion system andthe board to minimize noise generation and vibration transmission. Asnoted above, in some embodiments, a coupling between the propulsion pod150 and the strut 130 may be substantially rigid, such as by bolting thepropulsion pod 150 directly to the strut 130, or by forming the strutand propulsion pod housing as an integral structure. This rigid couplingallows for minimal movement of the strut 130 relative to the propulsionpod 150 other than deformation of the structural elements themselves. Insuch an embodiment, vibrations generated by operation of the propulsionpod 150 may be transmitted directly to the strut 130, and from there tothe board 110 and a rider seated thereon. The transmissions may occuralong a number of connected paths, including direct connections betweenthe strut 150 and the board 100, and indirect connections between thestrut 150 and the board 110 through intermediate components.

FIG. 2A is a partially exploded perspective view of a hydrofoilwatercraft such as the hydrofoil watercraft of FIG. 1A, illustrating amodular design of certain components of the hydrofoil watercraft. FIG.2B is a perspective view of the propulsion assembly and battery pack ofthe hydrofoil watercraft of FIG. 2A, shown in a detached state. FIG. 2Cis a perspective view of the propulsion assembly and battery pack of thehydrofoil watercraft of FIG. 2A, shown in an assembled state.

In some embodiments, a power source for the hydrofoil watercraft 200 maybe disposed within a discrete component which is separable from theboard 210. In the illustrated embodiment, the hydrofoil watercraft 200includes a battery pack 220 dimensioned to be retained within a recess216 within the board 210. Although referred to as a battery pack 220,the battery pack 220 may include any other suitable components inaddition to battery cells or other components capable of storing power,including control circuitry, sensors, transceivers, memory, or othercomponents. The battery pack 220 may therefore be a discrete componentwhich can be detached from the propulsion assembly 260 which includesthe strut 230 and the other components, such as propulsion pod 250.

The battery pack 220 can have an upper surface which is generallycoplanar with the upper surface 214 of the board 210, such that thebattery pack 220 cooperates with the surrounding portion of the board210 to form a surface upon which a rider can stand. In the illustratedembodiment, the recess includes at least one aperture extending to thelower surface of the board and allowing the strut 230 to be attached tothe battery pack 220 therethrough.

In some embodiments, the upper end of strut 230 may include a plugcomponent 222 configured to be placed in a mating configuration with aplug component 224 on a lower surface of the battery pack 220. In theillustrated embodiment, the plug component 222 of the strut 230comprises a plug, and the plug component 222 of the battery pack 220includes a corresponding receptacle, although in other embodiments, therelative locations of the plug and receptacle may be reversed.

In some embodiments, the upper end of strut 230 may include a mountingplate 232 supporting the plug component 222 and extending radiallyoutward beyond the edges of the plug component. The mounting plate maybe brought into contact with a mounting surface of the board 210, suchas the recessed mounting surface 218 of the board 210, and secured inplace by a plurality of rigid fasteners. Once the strut 230 is securedto the board 210, the battery pack 220 may be seated within the recess216 of the board 210, and the two plug components 222 and 224 may beconnected to connect the battery pack 220 to the propulsion assembly260.

Although the electric motor of propulsion pod 250 may be quieter thaninternal combustion engines used by other watercraft, the operation ofthe propulsion pod 250 will nevertheless generate noise and vibration.The vibration generated by the propulsion pod 250 will be conducted fromthe propulsion pod 250 to the strut 230. The vibration will then beconducted directly to the board 210 via the rigid connection between themounting plate 232 of the strut 230 and the mounting surface 218 of theboard 210. In addition, because the wiring connecting the propulsion pod250 to the battery pack 220 may be thick, vibrations will also betransmitted from the propulsion assembly 260 to the battery pack 220 viathe plug connection, and from the battery pack 220 to the surroundingboard 210.

The modular design of the hydrofoil watercraft 200 will affect thepropagation of vibrations within the components of the hydrofoilwatercraft 200. In particular, because the battery pack 220 may besubstantially denser than the surrounding board 210, the large mass anddensity of the battery pack 220 may reflect vibrations transmitted upthe strut 230 back down the strut 230. By concentrating much of theweight of the board 210 in a discrete, central structure adjacent thestrut 230, the overall amount of vibration transmitted to thesurrounding board 210 is reduced.

However, additional components can be used to reduce vibrationtransmission at each of these attachment points. For example, whilehigh-gauge wiring used to transmit power from the battery pack 220 tothe propulsion pod 250 will conduct vibration, the use of an elastomericmaterial in the mating components of one or both of the plug components222 and 224 can reduce the amount of vibration transmission from thestrut 230 to the battery pack 220. In addition, the use of anelastomeric material can also facilitate the formation of a watertightseal between the two plug components 222 and 224.

FIG. 3A is a perspective view of another embodiment of a propulsionassembly which includes an elastomeric vibration isolating component. Inparticular, the propulsion assembly 360 is similar to the propulsionassembly 260 of FIG. 2A but differs in that the mounting plate 332 ofthe strut 330 includes an elastomeric sheet 392 surrounding the plugcomponent 322. When the strut 330 is attached to the board, theelastomeric sheet 392 will be retained between the mounting plate 332and the corresponding mounting surface of the board, preventing directcontact between the mounting plate 332 and the mounting surface of theboard. By forcing the vibration to be transmitted through theelastomeric sheet 392 and through the comparatively smaller rigidfasteners securing the propulsion assembly 360 to the board, the amountof vibration transmitted from the strut 330 to the board will bereduced. [Representative details needed:

In the illustrated embodiment, the elastomeric sheet 392 is a singlecontiguous structure, but may include contours, cutouts, or otherfeatures not specifically illustrated. In other embodiments, however, aplurality of elastomeric structures may be used in place of a singleelastomeric sheet 392. In other embodiments, the elastomeric sheet maybe positioned on the mounting surface of the board, rather than themounting plate 332 of the strut 330.

FIG. 3B is a perspective view of another embodiment of a battery packwhich includes an elastomeric vibration isolating component. Inparticular, the battery pack 320 is similar to the battery pack 220 ofFIG. 2A but differs in that the battery pack 320 includes one or moreelastomeric sections 394 configured to contact an interior surface ofthe corresponding recess in the board. In the illustrated embodiment,the battery pack 320 includes elastomeric sections 394 on each of theside surfaces of the battery pack 320, as well as the lower surface ofthe battery pack 320, so that any portion of the battery pack 320 whichis in contact with the walls or base of the recess in the board has aportion of an elastomeric section 394 between the battery pack 320 andthe adjacent inner surface of the recess.

By including elastomeric vibration isolating components in some or allof the connection points between the strut and the board, between thestrut and the battery pack, and between the battery pack and the board,the transmission of vibrations from the strut to the board can bereduced. However, in the absence of further vibration isolation, a rigidconnection between the propulsion pod and the strut will result invibrations being transmitted to the strut, and may be amplified by theboard or other components of the hydrofoil watercraft if a forcingfrequency is generated at a natural resonance of a component of thehydrofoil watercraft. In some embodiments, vibration isolatingcomponents can be included closer to the propulsion pod which is thesource of the vibration. By including vibration isolating componentscloser to the source of the vibration, the provide vibration isolationcan be more effective.

In some embodiments, an adapter structure may be used to form part of acoupling between a strut and a propulsion pod. Such an adapter structuremay, for example, further define the shape of a channel extendingthrough the strut to provide an aperture or channel having a widercross-sectional dimension near the outer edges of the aperture orchannel than near the center of the aperture or channel. Such an adapterstructure may also be used to extend the length of an aperture orchannel extending through the strut.

FIG. 4A is an exploded isometric view of a strut with an adaptive clampshown. FIG. 4B is another exploded view of the strut and adaptive clampof FIG. 4A. FIG. 4C is an assembled view of the strut and adaptive clampof FIG. 4A.

The strut 430 includes first and second adaptive clamp components 462 aand 462 b on either side of the strut 430. Each of the first and secondadaptive clamp components 462 a and 462 b include a plurality ofapertures 464 extending therethrough. The apertures 464 are configuredto be aligned with corresponding apertures 438 extending through thestrut 430.

In the illustrated embodiment, the apertures 464 in the first and secondadaptive clamp components 462 a and 462 b have a first cross-sectionaldiameter 466 a in an interior portion of the apertures 464 configured tobe positioned adjacent the strut 430, and a second, larger,cross-sectional diameter 466 b in an exterior portion of the apertures464 further from the strut 430. The transition between the firstcross-sectional diameter 466 a and the second cross-sectional diameter466 b can be abrupt, such that the apertures 464 include an internalabutment surface 468 which may be generally parallel to the surface ofthe strut 430. As discussed in greater detail below, the internalabutment surface 468 may be configured to contact a facing surface of anelastomeric bushing to provide a restoring force inhibiting rotation ofthe strut relative to a propulsion pod coupled thereto. Each aperture464 provides an internal abutment surface 468 on either side of thestrut 430.

In other embodiments, however, as discussed in greater detail elsewhereherein, apertures may be formed directly in the strut itself, and may insome particular embodiments have multiple cross-sectional diameters. Insome particular embodiments, the apertures with multiple cross-sectionaldiameters may be more easily formed when the strut is formed at leastpartially using a molding or casting process, rather than when anextrusion process is used to form a strut.

In embodiments in which the propulsion pod is directly and rigidlycoupled to the strut, one or more bolts or screws extending through thepropulsion pod and the strut may be used to couple the strut to thepropulsion pod. In such embodiments, a bolt head and nut may bepositioned on opposite sides of the strut, and the nut tightened on thebolt to retain the propulsion pod in a rigidly coupled relationshiprelative to the strut. In other such embodiments, a screw may engageinternal threading of one or both of the strut and/or propulsion podhousing to rigidly couple the strut relative to the propulsion podhousing. In these embodiments, apertures having a substantially constantcross-section may extend through the strut and propulsion pod and bealigned with one another to receive a bolt or screw, and the use ofadaptive clamp components such as first and second adaptive clampcomponents 462 a and 462 b may be unnecessary, as there may be no needto define apertures having a varying cross-sectional shape. However, theuse of adaptive clamp components can facilitate the use of alternativecoupling mechanisms discussed in greater detail herein.

In some embodiments, an elastomeric vibration isolating component may bedisposed between the propulsion pod and the strut. By disposing theelastomeric vibration isolating component between the propulsion pod andthe strut, the vibration isolating component can inhibit vibrations frombeing transmitted to the strut, rather than inhibiting the transmissionof vibrations from the strut to the board and other intermediatecomponents.

In some particular embodiments, vibration isolation structures can bedisposed between the propulsion pod and the strut, forming a flexiblecoupling between the propulsion pod and the strut. In particular,vibration isolation structures may be used to provide an anisotropicallyflexible coupling between the propulsion pod and the strut. Such avibration isolation structure can be used to control the degree offlexibility in various directions. The vibration isolation structurescan provide a significant amount of vibration isolation in comparison toa rigid coupling. Such vibration isolating structures can be configuredto have a minimal effect on the responsiveness of the hydrofoilwatercraft to weight-shifted control of the hydrofoil watercraft.

In some embodiments, an anisotropically flexible coupling mechanism caninclude one or more elastomeric bushings configured to prevent directcontact between rigid portions of the propulsion pod and the strut. Aplurality of such elastomeric bushings can be configured to define adesired anisotropically flexible coupling between the strut and thepropulsion pod.

FIG. 5A is a perspective view of an embodiment of an elastomeric bushingwhich can be used as part of a flexible coupling between a propulsionpod and a strut. FIG. 5B is an isometric exploded assembly view of theelastomeric bushing of FIG. 5A. FIG. 5C is a front view of theelastomeric bushing of FIG. 5A. FIG. 5D is a cross-sectional view of theelastomeric bushing of FIG. 5A, taken along the line D-D of FIG. 5C.

The elastomeric bushing 580 has an outer cross-sectional shape whichincludes a beveled shoulder 584 which tapers to an outer face 582 a ofthe elastomeric bushing 580. The beveled shoulder 584 reduces thesurface area of the outer face 582. Inward of the beveled shoulder 584,an outer sleeve portion 586 a is partially separated from and overlapswith an inner sleeve portion 586 b, the outer sleeve portion terminatingin an inner abutment surface 582 b. An overmolding process may be usedto form the elastomeric bushing 580, joining discretely molded partstogether. In other embodiments, however, any other suitable fabricationmethod may be used to form the elastomeric bushing.

The elastomeric bushing 580 may in some embodiments not be formedentirely of an elastomeric material. For example, in the illustratedembodiment, the inner sleeve portion 586 b has an internal rigid sleeve588 extending therethrough. The internal rigid sleeve may have asubstantially constant inner diameter, and an outer diameter whichincludes outwardly extending features configured to engage correspondingfeatures on the interior of the inner sleeve portion 586 b, preventingslippage of the internal rigid sleeve 588 relative to the elastomericcomponents of the elastomeric bushing. In the illustrated embodiment,the internal rigid sleeve 588 extends the entire length of theelastomeric bushing 580, from the inner face 582 c to the outer face 582a.

In some embodiments, a plurality of elastomeric bushings may be used toform a flexible coupling mechanism for coupling the propulsion pod tothe strut. A pair of elastomeric bushings may be axially aligned withone another, with the outer faces of each bushing facing outwards onopposite side of the bushing arrangement. A through-pin may be insertedthrough the pair of axially aligned elastomeric bushings, with thethrough-pin extending through and contacting the rigid inner sleeves ofthe elastomeric bushings. The through-pin may be secured at each endrelative to the housing of the propulsion pod. The interior faces of theelastomeric bushings may be in contact with one another to define asubstantially contiguous cylindrical elastomeric structure extendingthrough an aperture in the strut.

FIG. 6A is an exploded isometric view of an embodiment of a propulsionassembly in which a propulsion pod is secured to a housing via aplurality of vibrationally-isolated through-pins. FIG. 6B is an explodedview from in front and above the embodiment of FIG. 6A. FIG. 6C is anisometric view of the assembled propulsion assembly of FIG. 6A. FIG. 6Dis a cross-sectional view of the assembled propulsion assembly of FIG.6C, taken along a plane extending through the longitudinal axes of twovertically aligned through-pins. FIG. 6E is a detail cross-sectionalview of section B of FIG. 6D.

In the embodiment of FIGS. 6A to 6E, an anisotropically flexiblevibration isolating coupling structure 670 is used to flexibly couple apropulsion pod to a strut 630 in the propulsion assembly 660. In theillustrated embodiment, the coupling structure 670 includes adaptiveclamp components 662 a and 662 b disposed on either side of the strut630. First and second housing sections 658 a and 658 b of the propulsionpod are located outward of the adaptive clamp components 662 a and 662 bon either side of the strut 630. Apertures 674 in the first and secondhousing sections 658 a and 658 b are axially aligned with thecorresponding apertures 664 extending through each of the first andsecond adaptive clamp components 662 a and 662 b. The anisotropicallyflexible vibration isolating coupling structure 670 also includesthrough-pins 672 (see FIG. 6B)

In some embodiments, the cross-sectional diameter of the apertures 674of the first and second housing sections 658 a and 658 b may be smallerthan the smallest cross-sectional diameter of the apertures 664 of thefirst and second adaptive clamp components 662 a and 662 b. Because thethrough-pins 672 may be rigidly coupled to the first and second housingsections 658 a and 658 b, the apertures 674 can have a cross-sectionaldiameter which is only slightly larger than the shank of the through-pin672. However, because the through-pins 672 are vibrationally isolatedfrom the first and second housing sections 658 a and 658 b and the strut630, the apertures 664 in the housing sections 658 a and 658 b and theapertures 638 in the strut 630 are larger, to accommodate at least theportions of the elastomeric bushings 680 inward of the inner abutmentsurfaces 682 b.

Through-pins 672 are inserted through each of the apertures 664 of thefirst and second adaptive clamp components 662 a and 662 b and thecorresponding apertures 638. Elastomeric bushings 680 are positioned onthe through pins 672 on opposing sides of the strut 630, between thecorresponding adaptive claim component and propulsion pod housingsection. The through-pins 672 extend through the rigid inner sleeves ofthe elastomeric bushings 680, such that each through-pin is suspended bya pair of elastomeric bushings 680 on either side of the through-pin.The elastomeric portions of the elastomeric bushings 680 are in contactwith the interior surfaces of the apertures 664 of the first and secondadaptive clamp components 662 a and 662 b. In the illustratedembodiment, as can be seen in FIGS. 6D and 6E, the inner faces of eachpair of elastomeric bushings 680 abut one another. In other embodiments,however, there may be some spacing between the inner faces of theelastomeric bushings 680 without allowing the rigid through-pin 672 tocome into contact with a rigid portion of the strut 630 or the first andsecond adaptive clamp components 662 a and 662 b.

The through-pins 672 may be directly in contact with rigid portions ofthe first and second housing sections 658 a and 658 b. The through-pins672 may be secured in place relative to the first and second housingsections 658 a and 658 b by any suitable mechanism. In the illustratedembodiment, a through-pin 672 is be inserted through one of the firstand second housing sections 658 a and 658 b, and a nut may be threadedonto a distal tip of the through pin 672, opposite the head of thethrough-pin 672, such that the nut and the head of the through-pinretain the first and second housing sections 658 a and 658 b relative toone another, with the propulsion pod suspended on the strut 630 via thevibrationally-isolated through pins 672.

In other embodiments, a through-pin 672 may be inserted through one ofthe first and second housing sections 658 a and 658 b and the distal tipof the through-pin 672, located away from the head of the through-pin672, may be screwed into a threaded aperture in the other of the firstand second housing sections 658 a and 658 b. In other embodiments, anaxially extending threaded aperture may be located at one or both endsof the through-pin, and a retaining screw may be inserted through one ofthe first and second housing sections 658 a and 658 b and screwed intothe axially extending threaded aperture. Any other suitable retentionmechanism may also be used, such as a cotter pin or similar structurelocated outward of at least a portion of one of the first and secondhousing sections 658 a and 658 b.

In the illustrated embodiment, the structure also includes a pair ofvibrationally coupled through-pins 672 which extend through grooves inthe motor endbell 606, vibrationally coupling the endbell 606 to thehousing of the propulsion pod. In other embodiments, however, asdescribed in greater detail elsewhere herein, these additionalvibrationally coupled through-pins 672 may be omitted, such that theendbell 606 is not directly coupled to the housing of the propulsionpod.

In addition, it can be seen in the illustrated embodiment that gaps 696are provided between the first and second adaptive clamp components 662a and 662 b and the first and second housing sections 658 a and 658 b,respectively, at the points at which the strut passes through the outerhousing of the propulsion pod housing. The gaps 696 may be dimensionedto prevent direct vibrational coupling between the strut 630 and thepropulsion pod housing, even when the strut 630 is canted relative tothe propulsion pod housing in response to an applied load. In theabsence of appropriately dimensioned gaps 696, the rigid portions of thehousing might be brought into contact with the rigid strut, providing anadditional direct vibrational transfer path which is not mitigated bythe elastomeric bushings.

To further mitigate the risk of such vibrational transfer, one or bothof the facing surfaces of the first and second housing sections 658 aand 658 b and/or the first and second adaptive clamp components 662 aand 662 b may be lined with an elastomeric material or includeelastomeric projections (not shown). If an additional vibrationaltransfer path is formed by contact between the strut and the propulsionpod housing, the elastomeric material may mitigate or reduce themagnitude of the vibration transmission.

Although a wide variety of types and shapes of elastomeric bushings orsimilar structures may be used to vibrationally isolate the strut fromthe propulsion pod, the elastomeric bushing may be in some embodimentsbe configured to control or define a desired force feedback response ofthe elastomeric bushing to flexure of the strut relative to thepropulsion pod. In particular, the beveled outer shoulder 584 of thebushing of FIG. 5A, which tapers to an outer face 582 a having acomparatively smaller surface area, can provide a progressive forcefeedback profile which increases in a non-linear fashion in response toan increased applied load. This increase may be, for example,exponential over at least a portion of the force feedback profile.

For example, when a small load is applied to the strut, application ofthe load will result in a comparatively small degree of rotation of thestrut relative to the roll or pitch axis of the hydrofoil watercraft.Because the through-pins 672 are rigidly coupled to the propulsionhousing, the through-pins 672 will cant slightly within the apertures664 within the first and second adaptive clamp components 662 a and 662b. The strut roll will result in compression between a propulsion podhousing section and an adaptive clamp section of an upper portion of oneof the elastomeric bushings 680 of each axially aligned pair ofbushings. The strut roll will also result in a compression between theopposite propulsion pod housing section and adaptive clamp section of alower part of the other elastomeric bushing 680 of each axially alignedpair.

The compression of the abutment surfaces of the adaptive clamp sectionsagainst the inner abutment surfaces 682 b of the elastomeric bushingswill compress the outer portion of the elastomeric bushing 680 as theouter portion of the elastomeric bushing will be squeezed between theabutment surface of adaptive clamp section and the inner surface of thepropulsion pod housing. The restoring force of the compressedelastomeric bushing section will counter the strut roll. For smallamounts of strut roll, the resulting restoring force will be small, duein part to the design of the outer profile of the elastomeric bushing680 and the facing interior surface of the first and second housingsections 658 a and 658 b While the outer face 682 a may abut or bepositioned close to the facing interior surface of the housing section,there may be greater clearance between the beveled shoulder 684 and thehousing section, allowing a degree of deformation of the elastomericbushing into the clearance between the beveled shoulder 684 and thehousing section. The flexible coupling provided by the anisotropicallyflexible vibration isolating coupling structure 670 may thereforeprovide a comparatively smaller amount of resistance over a narrowinitial range of strut roll, for example.

As the magnitude of the loading increases, and the beveled shoulder 684is also compressed against the facing interior surface of the housingportion, further deformation of the elastomeric bushings 680 results inan increase in the magnitude of the restoring force provided by theelastomeric bushings 680. Due to the design of the elastomeric bushings680, this increase in restoring force with increased loading isnon-linear. In particular, the resistance to further strut roll and/orpitch can increase substantially with increased flexure of the strutrelative to the propulsion pod increases. This non-linear force feedbackprofile can allow some strut roll and/or pitch within a narrow range,while inhibiting or preventing further strut roll and/or pitch beyondthat range.

The shape of the elastomeric bushings 680 may also provide otherstructural benefits. For example, the tapered shape of the elastomericbushings 680 can reduce or mitigate the likelihood of buckling of thebushing shoulder under heavy loads. The tapered shape of the elastomericbushings 680 can help to maintain the shape of the bushing during highforce conditions, reducing the likelihood of failure due to bucklingwhich can more easily occur if the outer portion of the elastomericbushing 680 were to have a more cylindrical profile. Furthermore, evenif buckling occurs, the tapered shape of the elastomeric bushings 680provides greater control over the shape of the elastomeric bushing 680under buckling conditions.

In addition to the design of the elastomeric bushings 680, other aspectsof the design of the anisotropically flexible vibration isolatingcoupling structure 670 can be used to control the degree of flexibilityin various directions. For example, in the illustrated embodiment, thelongitudinal spacing between the fore and aft sets of through holes isgreater than the vertical spacing between the upper and lower sets ofthrough holes.

For a radially symmetric elastomeric bushing, a given degree of strutroll will result in a smaller amount of deformation of the elastomericbushings than would the same degree of strut pitch. The hole pattern canbe used to provide a desired balance between strut roll flexibility andstrut pitch flexibility. Altering the hole pattern can change thebalance between resistance to strut roll and resistance to strut pitch.

In addition, the restoring force exerted by the elastomeric bushings maybe adjusted based on an axially compressive force applied to theelastomeric bushings from the through pins and their securementmechanisms. For example, if a through pin extends through each side ofthe propulsion pod housing to contact a threaded nut on the other side,the nut can be tightened or loosened to control the compressive forceapplied to the elastomeric bushings in the absence of strut roll and/orpitch. If this compressive force is increased, the elastomeric bushingmay be more resistant to additional strut roll and/or pitch, while ifthe compressive force is decreased, the elastomeric bushing may be lessresistant to additional strut roll and/or pitch. The securement of thethrough-pins can provide a way to tune the flexibility of the vibrationisolating coupling without altering the design or structure of thecoupling.

In some embodiments, the anisotropically flexible vibration isolatingcoupling structure 670 may be asymmetrically designed, such as tocompensate for the effect of motor operation on strut roll. Because themotor and propeller of the propulsion pod will spin in a givendirection, the strut may be under an asymmetrical load due to theresulting moment applied to the propulsion pod about the rotational axisof the roll axis of the hydrofoil watercraft. The magnitude of theapplied moment will increase as the propeller speed increases.

In embodiments in which the strut is rigidly coupled to the propulsionpod, this applied moment may have a minimal effect on the operation ofthe hydrofoil watercraft. However, in embodiments in which the couplingbetween the strut and the propulsion pod has some degree of flexibility,particularly when some degree of strut roll is permitted by the flexiblecoupling, the added moment applied due to operation of the propulsionpod may cause an asymmetry in the resistance to strut roll in oppositedirections. In some embodiments, an anisotropically flexible vibrationisolating coupling structure 670 may have an asymmetric design tocompensate for the propulsion pod moment. This asymmetrical design mayinclude, for example, varying the design of the elastomeric bushingsand/or facing interior surface, such as an arrangement in which the topright and lower left bushings being configured to provide a greaterrestoring force, In other embodiments, Elliptical or radial offsetdesigns may be used for bushings and/or for through-holes receivingbushings. In other embodiments, an asymmetrical taper may be provided ona through-pin. In other embodiments, further adjustments may be made tocompensate for an expected asymmetrical load, such as by providing gaps696 of different widths on either side of the strut 630 with differentwidths

FIG. 7 is a front view of a hydrofoil watercraft undergoing strut rollrelative to the propulsion housing. In a weight-shift controlledwatercraft such as hydrofoil watercraft 700, the watercraft may undergostrut roll as a function of the rider shifting their weight relative tothe board to control the operation of the watercraft. In contrast todesigns in which the strut is rigidly coupled to a propulsion pod, andthe orientation of the strut 730 relative to the propulsion pod 750 ismaintained even when the hydrofoil watercraft 700 rolls to one side oranother, a vibration isolating flexible coupling between the strut andthe propulsion pod can allow additional strut roll relative to thepropulsion pod when the hydrofoil watercraft 700 rolls to a given side.

As shown in FIG. 7, the strut 730 of the hydrofoil watercraft 700 isoriented at an overall angle Θ to the normal. The angle Θ is acombination of the overall roll angle α of the propulsion pod 750relative to the normal, and an additional strut roll angle β relative tothe propulsion pod 750. The range of additional strut roll angle β willbe dependent on the design of the elastomeric bushing and othercomponents of the hydrofoil watercraft but may in some embodiments beconfigured to be less than 3 degrees.

FIG. 8A is an exploded isometric view of another embodiment of apropulsion assembly in which a propulsion pod is secured to a housingvia a plurality of vibrationally-isolated through pins. FIG. 8B is anexploded front view of the embodiment of FIG. 8A. FIG. 8C is anisometric view of the assembled embodiment of FIG. 8A.

The propulsion assembly 860 is similar to the propulsion assembly 660 ofFIG. 6A but differs in two significant ways. In particular, thepropulsion assembly 860 does not include discrete adaptive clampstructures configured to be coupled to the strut to further definethrough-holes 838 for the through-pins 872 and elastomeric bushings 880.Instead, the strut 830 includes an integral thicker connection portion832 which defines channels 838 extending therethrough, similar to thechannels formed by the combination of through holes 638 and apertures664 in the propulsion assembly 660 of FIG. 6A.

In some embodiments, an adaptive clamp structure may be used inconjunction with struts having substantially constant cross-sections,such as metallic struts which may be formed by an extrusion process.Embodiments which include an integral thicker connection portion, suchas connection portion 832 of FIG. 8A, can include struts formed in amolding or casting process, such as carbon fiber struts which may bemore readily fabricated in shapes which have a varying cross-sectionalshape along their length.

The propulsion assembly 860 also differs from the propulsion assembly660 of FIG. 6A to 6E in that the propulsion assembly 860 does notinclude a plurality of vibrationally coupled bolts which rigidly couplethe motor endbell 806 to the first and second housing sections 858 a and858 b of the propulsion pod. Instead, as the motor endbell 806 is notdirectly coupled to the housing of the propulsion pod, the vibrationaltransfer path may run directly to the first and second housing sections658 a and 658 b from the motor and propeller 802, rather than passingthrough the endbell 806, in contrast to the embodiment of FIG. 6A.

It can also be seen in FIGS. 8A and 8B that the through-pins 872 differin their structure and manner of securement from the through pins 672 ofFIG. 6A. In the embodiment of FIG. 8A, the through-pins 872 have asubstantially constant outer cross-sectional shape, and are retainedwholly between the first and second housing sections 858 a and 858 b ofthe propulsion pod, rather than extending through at least one of thefirst and second housing sections 858 a and 858 b. Instead, axiallyextending threaded apertures are located in each end of the through-pin872 and retaining screws 876 may be inserted through each of the firstand second housing sections 858 a and 858 b and screwed into the axiallyextending threaded apertures of the through-pin 872.

While the embodiment of FIGS. 8A to 8C includes a strut having integralthickness variations and omits a rigid coupling between the propulsionpod housing components and the motor endbell, other embodiments mayinclude a wide variety of other design combinations. For example, insome embodiments, a strut having integral thickness variations may beused in conjunction with vibrationally coupled connections between thepropulsion pod housing components and the motor endbell.

FIG. 9A is an exploded isometric view of another embodiment of apropulsion assembly in which a propulsion pod is secured to a housingvia a plurality of vibrationally-isolated through-pins. FIG. 9B is anexploded view from in front and above the embodiment of FIG. 9A. FIG. 9Cis an isometric view of the assembled propulsion assembly of FIG. 9A.FIG. 9D is a cross-sectional view of the assembled propulsion assemblyof FIG. 9C, taken along a plane extending through the longitudinal axesof two vertically aligned through-pins. FIG. 9E is a detailcross-sectional view of section D of FIG. 9D.

The design of strut 930 is similar to that of strut 830 of FIGS. 8A to8C and includes an integral thicker connection portion 932 which definesapertures 938 extending therethrough. However, the vibration isolatingcoupling structure 970 includes sleeves 962 a and 962 b configured to beinserted into the apertures 938 from either side of the strut 930. Thesesleeves 962 a and 962 b may in some embodiments be made from a differentmaterial than the remainder of the strut 930, such as a more materialwhich may be more resistant to wear. The sleeves 962 a and 962 b mayalso be used to adjust the dimensions of the apertures 938 extendingthrough the strut 930. The interior dimensions of the sleeves 962 a and962 b are dimensioned to receive a portion of the elastomeric bushings980. Thus, rather than a single clamping adapter assembly, a pluralityof discrete adapter components may be used, for a wide range ofpurposes. In the illustrated embodiment, the through-pins 972 have ahead at one end, and a shank dimensioned to extend through apertures 974in both of the propulsion pod housing sections 958 a and 958 b, andsecured to a threaded nut or other securement device on the oppositeside of the propulsion pod as the bolt head.

It can be seen in FIGS. 9D and 9E that the channel defined by sleeves962 a and 962 b extending through the strut 930 has a substantiallyconstant diameter, and that the outer portions of the sleeves 962 a and962 b extend radially outward to define abutment surfaces configured tocontact the elastomeric bushings 980. The abutment surfaces of thesleeves 962 a and 962 b adjacent the inner abutment surfaces 982 b ofthe elastomeric bushings 980 are on the outer surface of the strut 930,rather than being recessed within the strut 930. It can also be seen inFIG. 9E that the sleeves 962 a and 962 b include an outwardly projectingportion which is configured to engage a notch between the outer sleeveportion and the inner sleeve portion of the elastomeric bushing 980,although other embodiments may include a flat outer face of the sleeves962 a and 962 b.

FIG. 10A is an exploded isometric view of another embodiment of apropulsion assembly in which a propulsion pod is secured to a housingvia a plurality of vibrationally-isolated through pins. FIG. 10B is anexploded view from above and in front of embodiment of FIG. 10A. FIG.10C is an isometric view of the assembled embodiment of FIG. 10A.

The strut 1030 is similar to the strut 630 of FIG. 6A and is used inconjunction with adaptive clamp components 1062 a and 1062 b disposed oneither side of the strut 1030. First and second housing sections 1058 aand 1058 b of the propulsion pod are located outward of the adaptiveclamp components 1062 a and 1062 b on either side of the strut 1030.Through-pins are inserted through the apertures 1074 in the first andsecond housing sections 1058 a and 1058 b and the apertures 664extending through each of the first and second adaptive clamp components1062 a and 1062 b.

Like the propulsion assembly 860 of FIGS. 8A to 8C, the propulsionassembly 1060 does not include a rigid coupling between the propulsionpod housing sections 1058 a and 1058 b and the motor endbell 1006. Asthe motor endbell 1006 is not directly coupled to the housing of thepropulsion pod, a vibrational transfer path may run directly to thefirst and second housing sections 1058 a and 1058 b from the motor andpropeller, rather than passing through the endbell 1006.

Although propulsion assemblies embodying certain combinations offeatures have been specifically illustrated, embodiments including othercombinations of features may also be used. In many of the embodiments ofpropulsion assemblies discussed herein, the rigid components of thestrut are vibrationally isolated from the propulsion pod flexiblycoupled to the strut. This minimizes transmission of vibration from thepropulsion pod to the strut through the mounting structure, ultimatelyisolating the support platform and rider from a substantial amount ofvibration generated by the operation of the propulsion pod. Thesevibrational isolation structures may also result in a reduction in theamount of noise generated by the operation of the hydrofoil watercraft,and in particular the amount of noise generated in the range of humanhearing. Although the mounting components are vibrationally isolatedfrom one another, transmission of power from the battery pack throughthe strut to the electric motor may require a direct connection, and mayutilize thick wiring which may transmit some vibrations from the motorand/or propeller. However, any vibration transmitted through the thickpower wire may be minimal in comparison to the vibration that would betransmitted through a rigid, non-isolating mounting structure couplingthe propulsion pod to the strut.

Embodiments of vibration isolating mounts have been shown to beeffective at reducing noise generated by operation of a watercraft suchas an electric hydrofoil watercraft. FIG. 11A is a plot of measurednoise as a function of frequency, illustrating a reduction in noiseachieved by the use of a vibration isolating mounting structure incomparison to a non-isolating mounting structure. FIG. 11B is anotherplot of measured noise as a function of frequency, illustratingreductions in noise achieved by the use of vibration isolating mountingstructures in comparison to a non-isolating mounting structure. It canbe seen in each of these figures that the embodiments which include avibration isolating mechanism such as those described herein areeffective at reducing noise generated by the operation of thewatercraft, and in particular reducing noise within the range of humanhearing.

As discussed above, in some embodiments, a gap may be provided betweenthe strut and the propulsion pod housing sections, to prevent contactbetween rigid portions of the propulsion pod housing and rigid portionsof the strut. However, the inclusion of such a gap can affect thehydrodynamic profile of the propulsion pod and can have an impact onperformance of the watercraft.

In some embodiments, the propulsion pod may include additionalstructures configured to compensate for the presence of these gaps inthe propulsion pod housing. For example, in some embodiments, flexiblegaskets can be supported by one or both of the strut and the propulsionpod housing and be used to fill at least a portion of these gaps. If thegasket comprises an elastomeric material, vibration transmission throughthe gasket may be minimized, and the presence of an elastomeric gasketcan help to maintain separation between rigid portions of the strut andrigid portions of the propulsion pod housing, even at the edges of thestrut roll range. In other embodiments, the propulsion pod may includeone or more deflectors positioned fore of these gaps, to alter thehydrodynamic profile of the propulsion pod and minimize the effect ofthe gaps in the propulsion pod housing. Other suitable mechanisms mayalso be used.

Although the illustrated embodiments depict the propulsion assembly asbeing connected to a point on the strut between the hydrofoil and thesupport platform, other arrangements of the propulsion assembly andhydrofoil relative to the strut may be used in other embodiments. Forexample, in some embodiments, the propulsion pod may be attached at thebase of the strut, along with the hydrofoil, such as in the embodimentsshown in FIGS. 1 and 7B in the attached Appendix, and in other figuresin the attached Appendix. In such an embodiment, the hydrofoil may berigidly coupled to the strut, and the propulsion pod formed around aportion of the hydrofoil or a structure supporting the hydrofoil toallow the propulsion mechanism to be vibrationally isolated from thestrut.

In the illustrated embodiments, the vibration isolation structure whichisolates the motor and propeller and the strut is located at theconnection between the propulsion pod and the strut. However, in otherembodiments, the vibration isolation structure may be located within aportion of the propulsion pod located away from the strut. For example,an elastomeric sleeve or other isolating elastomeric structure may beformed around the motor and propeller within the propulsion pod,isolating those structures from the surrounding portions of thepropulsion pod and preventing contact between rigid components coupledto the motor and/or propeller and rigid components coupled to the strut.Such an elastomeric sleeve may be substantially larger in diameter thanthe elastomeric bushings of the illustrated embodiment.

FIG. 12A is a perspective view of a combination propulsion pod andhydrofoil structure, coupled to a strut at the base of the strut. FIG.12B is an exploded assembly view of the combination propulsion pod andhydrofoil structure of FIG. 12A shown detached from the strut. Thecombination propulsion pod and hydrofoil structure 1250 includes apropulsion pod fuselage housing 1212 which supports the front or mainfoil 1210 at the front of the housing 1212, and a rear foil 1208 at therear of the fuselage, beneath the propeller.

In such an embodiment, a vibration isolation structure need not belocated at the connection point between the strut 1230 and the housing1212 of the combination hydrofoil/propulsion pod 1250. Instead, thisconnection, which may also include a wiring connection 1204 forconnecting the wiring 1206 extending within the strut 1230 to internalwiring within the housing 1212, may be a rigid connection. The use of arigid connection may provide additional stability for the front and rearfoils 1210 and 1208, so that at least a portion of the housing 1212 isrigidly connected to the strut 1230. Vibration isolation which preventsvibration from being transmitted through support components from themotor and propeller to the strut 1230 may instead be located within thehousing 1212, aft of the strut 1230. This vibration isolating structuremay include an elastomeric material or sheath internal to the housing1212. For example, a larger elastomeric sheath may surround the motorand propeller within the housing, or the motor and propeller may be heldin place via a plurality of discrete elastomeric structures, such as aplurality of elastomeric pads or bumpers. Alternatively, the motor andpropeller, or a support frame supporting the motor and propeller, may besuspended at least partially within or behind the housing 1212 usingvibration isolating mounts similar to those described herein. One ormore elastomerically-sheathed through-pins or bolts may extend into oracross an internal cavity within the housing 1212, and support themotor, propeller, a supporting frame, or a motor/propeller assembly,while preventing or inhibiting direct contact with rigid portions of thehousing 1212.

FIG. 13 is a cross-sectional view schematically illustrating anotherembodiment of a combination propulsion pod and hydrofoil structure,coupled to a strut at the base of the strut. The strut 1330 includes aconnector 1308 at the upper end of the strut 1330, which is inelectrical communication with wiring 1306 extending the length of thestrut and connected to a drive 1302 within housing 1352. The drive 1302may include, for example, at least one of a motor, gearbox, andcontroller. In the illustrated embodiment, the wiring 1352 is routedthrough a nosecone 1354 of the housing 1352. A propeller 1316 issurrounded by a protective shield structure 1322 and driven by an axle1314 coupled to the drive 1302. In addition to supporting the drive 1302and propeller 1316, the housing 1352 also supports front foil 1310 andrear foil 1312 to provide a combination hydrofoil/propulsion pod 1350.Any suitable vibration isolating structures, such as vibration isolatingstructures at least partially internal to the housing 1352, may be usedto vibrationally isolate the drive 1302 and propeller 1316 to preventvibrations generated by operation of those components being conductedthrough support structures up the strut 1330 and to a support platformsuch as a hydrofoil board. The vibration conducted by directly connectedwiring 1306 may be minimal in comparison to the vibration which wouldotherwise be conducted via the support structures.

In some embodiments, non-structural methods of controlling noise andvibration may also be used, in place of or in addition to the structuralfeatures discussed herein. In some embodiments, the propulsion assemblymay be operated in a manner which alters the noise and vibrationgenerated by the operation of the hydrofoil watercraft. As discussedabove, the noise and vibrations generated during the operation of ahydrofoil watercraft are dependent in part on the resonant frequenciesof the various components of the hydrofoil watercraft. Because of thenatural resonance of these components, certain motor speeds, forexample, may generate forcing frequencies which result in substantiallymore noise and vibration than are generated at other motor speeds. Evena small change in motor speeds can result in a substantial difference ingenerated noise and vibration, by avoiding the generation of forcingfrequencies which align with the natural resonance of the hydrofoilwatercraft components.

In some embodiments, a motor controller may be configured to minimizeoperation at speeds which generate forcing frequencies corresponding toresonant frequencies of components of the hydrofoil watercraft. This maybe done, for example through the use of a nonlinear transition ratebetween motor speeds, to minimize the time spent operating at a motorspeed which may generate problematic forcing frequencies.

In some embodiments, the non-linear transition rate or other changes tothe operation of the motor controller may be at least partiallypredefined, with the motor controller configured to minimize time spentat speeds known or expected to generate problematic forcing frequencies.This determination may be made, for example, on the basis of analysis ofthe hydrofoil watercraft design. In other embodiments, however, thenon-linear transition rate or other changes to the operation of themotor controller may be at least partially dynamically determined orconfigured on the basis of a sensed response to operation of thespecific hydrofoil watercraft and arrangement.

In some embodiments, this may be done as part of an initial or periodicconfiguration, in which the noise and/or vibration generated by thehydrofoil watercraft is measured over a range of motor speeds, and anappropriate non-linear transition profile generated on the bases ofidentifying motor speeds which generate problematic forcing frequencies.In particular, motor speeds may be identified where the problematicforcing frequencies are generated over a comparatively small range ofmotor speeds which may be sped through quickly, to reach another motorspeed which generates less noise and/or vibration without a significantchange in motor speed. In other embodiments, adjustments to motorcontrol may be done in a dynamic fashion during operation of thecontroller, with real-time sensing of noise and/or vibration used toidentify increases in noise or vibration, and dynamically adjust thecontrol of the motor accordingly. This sensing can be performed bysensors internal to the hydrofoil watercraft itself, as well as by aseparate device, such as a smartphone or wearable device of a useroperating the hydrofoil watercraft in wireless or other communicationwith the hydrofoil watercraft.

Although described with respect to hydrofoil watercraft, vibrationisolating mounts incorporating some or all of the features describedherein may be used in a variety of other implementations, includingother types of watercraft. For example, in some embodiments, an outboardmotor may be suspended from a transom of a boat using a plurality ofvibration isolating mounts to form a flexible coupling mechanism whichisolates components which are rigidly coupled to the outboard motor fromcomponents which are rigidly coupled to the transom. In some particularembodiments, for example, these vibration isolating mounts may extendthrough apertures in the transom and be indirectly or directly rigidlycoupled to the outboard motor at locations on opposite sides of thetransom. A plurality of elastomeric bushings such as those discussedherein may be used to maintain vibration isolation of the outboardmotor. Similar vibration isolating mounts may be used in otherwatercraft, including personal watercraft such as jetskis and otherwatercraft devices with closed hulls, as well as boats and otherwatercraft configured to seat multiple passengers.

While certain embodiments have been described, these embodiments havebeen presented by way of example only and are not intended to limit thescope of the disclosure. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms. Furthermore, variousomissions, substitutions and changes in the systems and methodsdescribed herein may be made without departing from the spirit of thedisclosure. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope ofthe disclosure.

Features, materials, characteristics, or groups described in conjunctionwith a particular aspect, embodiment, or example are to be understood tobe applicable to any other aspect, embodiment or example described inthis section or elsewhere in this specification unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The protection is notrestricted to the details of any foregoing embodiments. The protectionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

Furthermore, certain features that are described in this disclosure inthe context of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresthat are described in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations, one or more features from a claimedcombination can, in some cases, be excised from the combination, and thecombination may be claimed as a subcombination or variation of asubcombination.

For purposes of this disclosure, certain aspects, advantages, and novelfeatures are described herein. Not necessarily all such advantages maybe achieved in accordance with any particular embodiment. Thus, forexample, those skilled in the art will recognize that the disclosure maybe embodied or carried out in a manner that achieves one advantage or agroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

Certain terminology may be used in the following description for thepurpose of reference only, and thus is not intended to be limiting. Forexample, terms such as “upper”, “lower”, “upward”, “downward”, “above”,“below”, “top”, “bottom”, “left”, and similar terms refer to directionsin the drawings to which reference is made. Such terminology may includethe words specifically mentioned above, derivatives thereof, and wordsof similar import. Similarly, the terms “first”, “second”, and othersuch numerical terms referring to structures neither imply a sequence ororder unless clearly indicated by the context.

Conditional language, such as “can,” “could,” “might,” or “may,” unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements, and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements, and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or without userinput or prompting, whether these features, elements, and/or steps areincluded or are to be performed in any particular embodiment.

Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

Terms relating to circular shapes as used herein, such as diameter orradius, should be understood not to require perfect circular structures,but rather should be applied to any suitable structure with across-sectional region that can be measured from side-to-side. Termsrelating to shapes generally, such as “spherical” or “circular” or“cylindrical” or “semi-circular” or “semi-cylindrical” or any related orsimilar terms, are not required to conform strictly to the mathematicaldefinitions of spheres, circles, cylinders or other structures, but canencompass structures that are reasonably close approximations.

The terms “approximately,” “about,” and “substantially” as used hereinrepresent an amount close to the stated amount that still performs adesired function or achieves a desired result. For example, in someembodiments, as the context may permit, the terms “approximately”,“about”, and “substantially” may refer to an amount that is within lessthan or equal to 10% of the stated amount. The term “generally” as usedherein represents a value, amount, or characteristic that predominantlyincludes or tends toward a particular value, amount, or characteristic.As an example, in certain embodiments, as the context may permit, theterm “generally parallel” can refer to something that departs fromexactly parallel by less than or equal to 20 degrees. As anotherexample, in certain embodiments, as the context may permit, the term“generally perpendicular” can refer to something that departs fromexactly perpendicular by less than or equal to 20 degrees.

The terms “comprising,” “including,” “having,” and the like aresynonymous and are used inclusively, in an open-ended fashion, and donot exclude additional elements, features, acts, operations, and soforth. Likewise, the terms “some,” “certain,” and the like aresynonymous and are used in an open-ended fashion. Also, the term “or” isused in its inclusive sense (and not in its exclusive sense) so thatwhen used, for example, to connect a list of elements, the term “or”means one, some, or all of the elements in the list.

Overall, the language of the claims is to be interpreted broadly basedon the language employed in the claims. The language of the claims isnot to be limited to the non-exclusive embodiments and examples that areillustrated and described in this disclosure, or that are discussedduring the prosecution of the application.

Although the invention has been disclosed in the context of certainembodiments and examples, it will be understood by those skilled in theart that this disclosure extends beyond the specifically disclosedembodiments to other alternative embodiments and/or uses of theembodiments and certain modifications and equivalents thereof. The scopeof the present disclosure is not intended to be limited by the specificdisclosures of preferred embodiments in this section or elsewhere inthis specification, and may be defined by claims as presented in thissection or elsewhere in this specification or as presented in thefuture.

What is claimed is:
 1. An anisotropically flexible coupling mechanism configured to flexibly couple a suspended component to a support member extending therethrough, the coupling mechanism comprising: a plurality of vibration isolating suspension mounts configured to extend through apertures in the support member, each of the vibration isolating suspension mounts comprising: a rigid internal member extending along a longitudinal axis; and an elastomeric sheath surrounding the axially extending member, the elastomeric sheath comprising: a radially inward portion surrounding the rigid internal member; and a radially outward portion spaced at least partially apart from the radially inward portion, the radially outward portion comprising an abutment surface configured to contact at least one of the support member or a component rigidly coupled to the support member.
 2. The coupling mechanism of claim 1, wherein the abutment surface of the elastomeric sheath is generally orthogonal to the longitudinal axis of the rigid internal member.
 3. The coupling mechanism of claim 1, wherein the apertures in the support member are generally parallel to one another and axially offset from one another.
 4. The coupling mechanism of any of claim 1, wherein the rigid internal member is configured to be rigidly coupled to the suspended component at two locations on opposite sides of the support member.
 5. A watercraft device, comprising: a support platform; a strut extending from the underside of the support platform; a hydrofoil connected to the strut; and a propulsion pod supported by the strut at a location in-line with or above the hydrofoil, the propulsion pod secured to the strut by an anisotropically flexible coupling mechanism including a plurality of vibrationally isolated mounts extending through the strut, each of the plurality of vibrationally isolated mounts rigidly coupled to the propulsion pod at two locations on opposite sides of the strut.
 6. The watercraft device of claim 5, wherein each of the plurality of vibrationally isolated mounts comprises: a rigid internal axially extending member configured to be rigidly coupled to the propulsion pod; and an elastomeric bushing radially outward of the axially extending member, the elastomeric bushing configured to retain the axially extending member, the elastomeric bushing comprising an inner abutment surface dimensioned to contact at least one of the strut or a retaining component rigidly coupled to the strut.
 7. The watercraft device of claim 6, wherein each of the plurality of vibration isolating mounts comprises: a first elastomeric bushing disposed at least partially on a first side of the strut; and a second elastomeric bushing disposed at least partially on a second side of the strut opposite the first side of the strut, wherein the first and second elastomeric bushings are axially aligned with one another, and the axially extending member extends through both the first and second elastomeric bushings.
 8. The watercraft device of claim 6, wherein each of the elastomeric bushings includes: a radially inward portion having a first cross-sectional diameter, the radially inward portion dimensioned to extend at least partially into a mounting aperture in the strut; and a radially outward portion comprising the inner abutment surface and having a second cross-sectional diameter greater than the first cross-sectional diameter, the radially outward portion comprising a beveled shoulder section.
 9. The watercraft device of claim 7, wherein the outer portion of each of the plurality of elastomeric bushings is shaped to provide a non-linear restoring force as the strut is rotated relative to the propulsion assembly about a roll axis of the propulsion hub.
 10. The watercraft device of claim 6, wherein each of the elastomeric bushings include an internal rigid sleeve surrounded by an elastomeric sleeve located radially outward of the internal rigid sleeve.
 11. The watercraft device of claim 5, wherein the anisotropically flexible coupling mechanism is configured to provide less resistance to rotation of the strut relative to the propulsion assembly about a roll axis of the propulsion assembly than to rotation of the strut relative to the propulsion assembly about a pitch axis of the propulsion hub.
 12. The watercraft device claim 5, additionally comprising a battery pack disposed at least partially within the support platform, additionally comprising an elastomeric material disposed between the battery pack and the support platform, wherein the coupling between the battery assembly and the strut reduces an intensity of vibrations transmitted to and attenuated by the support platform.
 13. The watercraft device of claim 5, additionally comprising an elastomeric material disposed between a mounting plate of the strut and a mounting surface on the underside of the support platform, the mounting plate of the strut coupled to the support platform by a plurality of rigid fasteners.
 14. The watercraft device of claim 5, wherein the watercraft device is configured to reduce generation of noise having frequencies in the range of 300 Hz to 3 kHz.
 15. The watercraft device of claim 5, further comprising a motor controller operably connected to the motor, the motor controller configured to provide a nonlinear transition rate between motor speeds, the nonlinear transition rate configured to minimize vibration generation, and wherein the nonlinear transition rate is a predetermined nonlinear transition profile which minimizes motor operation at speeds which generate forcing frequencies corresponding to resonant frequencies of components of the watercraft device.
 16. The watercraft device of claim 15, wherein the nonlinear transition rate is dynamically adjusted in response to generated vibration.
 17. A weight-shift controlled watercraft device, comprising: a board configured to support a rider thereon; a strut extending from the underside of the board, the strut having a hydrofoil supported at a lower end of the strut; a propulsion pod comprising: a propeller operably coupled to a driving motor; a housing, the strut extending through a portion of the housing, and a plurality of vibration isolating mounts flexibly coupling the propulsion assembly to the strut, each of the plurality of vibration isolating mounts comprising: a fastener extending from a first side of the strut to a second side of the strut through an aperture in the strut; and an elastomeric bushing surrounding at least a portion of the fastener, the elastomeric bushing in contact with at least one of the strut or a retaining component rigidly coupled to the strut to provide vibration isolation between the propulsion pod and the strut.
 18. The watercraft device of claim 17, wherein the plurality of vibration isolating mounts are configured to suspend the propulsion pod from the strut.
 19. The watercraft device of claim 17, wherein the plurality of vibration isolating mounts are configured to prevent direct contact between a mounting component rigidly coupled to the strut and a mounting component rigidly coupled to the propulsion pod.
 20. The watercraft device of claim 17, wherein the elastomeric bushing comprises an inner abutment surface configured to contact at least one of the strut or a retaining component rigidly coupled to the strut to provide a restoring force in response to roll of the strut relative to the propulsion pod about a rotational axis of a propeller of the propulsion pod, and wherein the inner abutment surface is radially spaced apart from a radially inward portion of the elastomeric bushing. 